As of 2008, approximately 81 million people in the US have diabetes or pre-diabetes. As complications arising from diabetes represent the single largest cost to the US health care system, it is an imperative public health crisis to develop better therapies that treat, and potentially cure, the underlying cause of diabetes: hyperglycemia resulting from insufficient insulin production, due to either autoimmune destruction of insulin-producing beta cells or an inadequate mass of functional insulin-producing beta cells. This application seeks to improve our understanding of how to increase beta cell mass by investigating the mechanisms that govern the expansion of beta mass during embryogenesis and in response to diet-induced insulin resistance. Specifically, we propose to investigate how mechanisms that govern the accumulation or degradation of p27, a protein that functions to inhibit the expansion of beta cell mass, can be exploited to expand beta cell mass. We propose that Spy1A, a cell novel cell cycle regulator that can bypass p27-mediated inhibition of cell expansion, can be overexpressed to increase beta cell mass. We have also identified that Rap1A, a small GTPase activated during beta cell differentiation, may induce cell cycle arrest by upregulation of p27. We will use transgenic mouse models to investigate if spy1A overexpression or rap1A deletion can increase beta cell mass. We have discovered previously unidentified roles for skp2 and p27 in enteroendocrine differentiation from gut progenitor cells, which will serve as an alternative in vivo model to understand how beta cells may differentiate from adult progenitor cells to expand beta cell mass. We will use purified cell populations, cell culture models, lentiviral transfections, and siRNA knockdown experiments to assess how these proteins activate or repress p27 transcription and degradation. We expect that the results from the proposed aims of this grant will directly contribute to potential therapies to regenerate functional beta cell mass for diabetic patients. The theme of this research directly addresses the Beta Cell Therapy Research Program programmatic thrust of the NIDDK's division of Diabetes, Endocrinology and Metabolic Diseases. The research proposed in this grant will foster the transition of Dr. Senta K. Georgia from junior faculty to an independent research career. The theme of this grant is an extension of her established publication record in the field of beta cell differentiation and regeneration. Though she is building on her previous publication record, the experiments proposed in this application expose her to new techniques and new model systems for understanding beta cell differentiation and expansion. Under the mentorship of Dr. Martn Martn and co-mentorship of Dr. Anil Bhushan, Dr. Georgia will pursue cutting edge research at UCLA, with access to state-of-the-art equipment, cores, and resources to facilitate the production and analysis of data. In addition to her research, this proposal outlines specific mentorship activities that will foster Dr. Georgia's independence, including (but not limited to) attendance at new investigator workshops, presentation of her work at relevant international conferences, and detailed benchmarking of her progress by a personalized career development plan. We expect that the research proposed in this application will result in 3 high impact publications within the next 5 years that will advance the field of regenerative medicine and islet biology. With protected research time, freedom from the responsibility of didactic teaching responsibilities, participation in intellectually stimulating and education seminars, exposure to new model systems and new techniques, immersion in a stimulating and supportive environment, and active mentorship to encourage critical assessment of data and publication, we are very confident that Dr. Georgia will be an outstanding candidate for a tenure track independent research position at the end of the granting period of this award. PUBLIC HEALTH RELEVANCE: The 81 million Americans that are diabetic or are pre-diabetic suffer from the condition because the body's insulin-producing cells, either because of autoimmune destruction or the inability of the cells to function properly, are unable to maintain normal blood sugar levels. The proposed studies are targeted to understand how functional insulin-producing cells normally reproduce themselves. Results from these studies will contribute to the design of therapies to generate more insulin-producing cells as an effective cure for diabetes.